The present invention generally relates to cardiac resuscitation devices which may be worn or carried by patients prior to the onset of any acute symptoms which may lead to a cardiac arrhythmia, etc. In particular, the present invention relates to the field of such apparatus which are intended to be carried by the patient either at all times or as often as possible, which devices are adapted through a telephonic interface to transmit information to a cardiologist begining at the onset of cardiac symptoms.
Of the approximately 500,000 coronary deaths each year in the USA, 50-70% are sudden deaths (defined as death within 24 hours of onset of acute symptoms) outside the hospital. The cause of death in most of these patients was a potentially treatable cardiac arrest due to a ventricular arrythmia. The coronary care unit experience has almost eliminated arrythmias as a cause of death once the patient comes within its confines because many arrythmias are prevented and the ones that occur are rapidly treated with cardiopulmonary resuscitation and defibrillation. Unfortunately, there are technical and logistical problems in preventing or treating a cardiac arrest rapidly in victims outside the hospital setting because of the speed of their occurrence. A Maryland study found that 40% of cardiac arrests occurred within 15 minutes of the onset of the patient's symptoms, 60% occurring within 1 hour, and 80% of arrests occurring within 4 hours of symptoms. 63% of these cardiac arrests occurred at the victims home, 5% at work, and the remainder at miscellaneous locations. Considering that the mean time between onset of acute coronary symptoms and the patients arrival in the hospital emergency room has been estimated at 3.5 hours in the USA, most patients experience a cardiac arrest prior to arrival at a facility where it can be treated. This total time can be broken up into a decision time-the period between acute onset of symptoms to calling for an ambulance or deciding to seek medical help -- and a transportation time -- the time it takes an ambulance suitably equipped with resuscitation equipment to arrive at the patient's location once called, or an unequipped ambulance to arrive at the patient's location and transport the victim to a suitably equipped hospital emergency room. The decision time has been estimated at 200 minutes and the transportation time at 30-40 minutes in a review of the reported literature. Currently, some municipalities have organized fast reaction rescue teams which have reduced the transportation time to as low as 5 to 15 minutes. This is particularly true where the financial resources are available to utilize mobile coronary care units manned by M.D.'s and/or paramedics or rescue squads capable of defibrillating victims on the "go ahead" from hospital based physicians receiving the patients "EKG" via telemetry. Unfortunately, this approach is expensive and the speed of arrival, and therefore, survival results are highly dependent upon geographic location, traffic conditions, population density and the number of mobile units in the system. Moreover, this approach does not reduce the average 200 minute patient delay in seeking medical aid unless combined with a population education program aimed at teaching the significance of the coronary symptoms, the urgency in seeking medical aid rapidly, and the overcoming of patient denial of the importance of chest pain because of fear of myocardial infarction and its consequences and the skills of cardiopulmonary resuscitation. For the reasons discussed above, educating patients and family members to reduce decision time in combination with the remote, telephonic cardiac resuscitative device to be discussed in detail herein, will provide safe, inexpensive and practical resuscitative coronary care within the brief length of time required in order to substantially increase the salvage rate of cardiac arrests occurring outside the hospital.
Prior art cardiac resuscitation or warning devices have, accordingly, generally been designed for use by mobile cardiac care units wherein a trained cardiac care team may defibrillate the patient with the aid of a portable defibrillator under the direction of a medical doctor. In U.S. Pat. No. 3,703,900, for example, a portable defibrillating apparatus is described wherein a U-shaped electrode current applicator with a handle and three electrodes may be applied to a patient which will sense for the presence of a normal heartbeat, indicate a poor contact, and, on command, activate a defibrillating device.
Alternatively, various prior art devices have been proposed for continuously monitoring a patient either in a hospital cardiac care unit or elsewhere for the purpose of determining the occurance of arrhythmias, cardiac arrest, etc. One such approach is illustrated in U.S. Pat. No. 3,724,455 wherein radio telemetry is employed to continuously monitor the EKG wave form which is recorded and/or which is analyzed to provide an alarm or otherwise signal to the patient what medication should be administered or what other action should be taken. In one embodiment, a signal may be transmitted by radio telemetry to activate, for example, a defibrillator which can be triggered by a central facility upon detection of ventricular fibrillation. Unfortunately, not only must the wearer maintain good electrode contact at all times, but should that contact be impaired or should the radio telemetry signal be interfered with, as for example, by entering large buildings constructed of steel or concrete, the quality of the signal transmitted by the device may mimic fibrillation or cardiac arrest, at which time the activation of the defibrillating device could cause the death of the wearer.
Alternatively, in U.S. Pat. No. 3,144,019 a cardiac monitoring device is disclosed for automatically monitoring a wide variety of cardiac arrhythmias or abnormalities and for automatically effecting electro-cardiographic recording thereof and for initiating and terminating appropriate treatment in response thereto. The device which is described therein is primarily intended for periods of prolonged observation especially necessary during cardiac surgical procedures and during a normal two day recuperating period after such operation during which time an arrhythmia is frequently the source of death. Upon sensing an arrhythmia, this apparatus is designed to automatically administer electric shock and/or to open the valves of drug circuits which are connected to a previously inserted IV.
While various other remote stimulators or injectors, such as those illustrated in U.S. Pat. No. 3,179,890 or 3,841,328 are known to the art of medical electronics, no practical device has yet been developed exhibiting adequate safeguards for the patient while at the same time delivering primary cardiac care within the length of time required in order to substantially increase the salvage rate of patients experiencing the onset of acute cardiac symptoms.